Multiple choice

The sum of two numbers is 528 and their HCF is 33. Find the number of such pairs.

  1. 2

  2. 3

  3. 5

  4. 4
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D Correct answer
Explanation

Let the numbers be 33a and 33b where a and b are coprime. Then 33(a+b) = 528, so a+b = 16. Coprime pairs summing to 16 are: (1,15), (3,13), (5,11), (7,9) and their reverses. This gives 4 pairs.

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